Reply To: Richard Branson – Virgin Pledge

[Jolly Roger]

Duke Leto wrote: 1) I’m not sure that the Helium stream would provide thrust with anything close to the efficiency that it provides deceleration electricity, since ion drives provide minimal constant acceleration over long distances.

You are right about the Helium exhaust not providing very much thrust. It just does not put through much mass. It is more effective powering a motorized fan/propeller to move large masses of air.

An FF rocket will not be a typical ion drive, however. It will have ~1,000 times more power. It may more closely resemble a plasma rocket like VASIMR.

To get out of Earth’s gravity well we need high thrust, and that means moving a lot of mass quickly. Maybe we could boil water with microwaves, or squirt salt water through a linear accelerator, or even a compressed air/water rocket.

2) I also gather from your description that the alpha stream would be going through the fan system, that would mean that the reactor must be located in the center.

I did not make myself clear. The reactor is located behind the motor, but only so that the electrical cable from the generator to the motor is short. The reactor and generator could just as easily be located somewhere else in the plane. The airflow from the fan does not go through the reactor. It goes around it, to provide cooling.

As the Helium exhaust will provide negligible thrust, we will now minimize it, turn the reactor around and place the decelerator/generator immediately behind the motor, and the reactor at the rear. The reactor, fuel and exhaust will be self-contained and separated from the environment.

I think this would mean that: …
c) You’d be shooting fully energized ionizing alpha particles into the environment, which I believe is nastier then Gamma.

We will now extract as much energy as possible from the Alpha stream and neutralize it with electrons. It may be worthwhile to save the helium and sell it. Unreacted fuel will be recycled back to the reactor.

Alpha particles are only hazardous if taken internally, as they steal electrons and break chemical bonds. Exposure to Alpha gas would damage the mouth, nose, throat and lungs.

Keep in mind I’m looking to have engines that fit into existing vehicles without too much fuss, not next generation machines.

To retrofit existing aircraft, reactor/motor/fan pods can be made to replace wing-mounted turbofan engines on the larger planes. Tail-mounted engines will be more complicated to replace, but possible. The existing fuel tanks will be drained, cleaned, dried and removed if possible. Reactor fuel tanks will be small enough to include in the engine pods.

Medium-sized aircraft will have the reactor/generator placed in the fuselage, with electrical cables to the replacement motor/fan pods on the wings.

Aircraft too small for a reactor will be converted to fuel cell or electric vehicles.

Next generation aircraft will be more efficient than retrofitted ones.